The present invention relates to a hydraulically damped elastic bearing.
Such bearings comprising a loose piece for uncoupling vibrations are commonly known in the state of the art for numerous disclosures of different embodiments. A loose piece in such a bearing may be a disc or annular disc. In fact it is disposed loosely in a cavity or a disc-shaped material configured in a different manner which is vibratory, especially vibratory in axial direction with respect to its main surfaces, and which is restrained in a safety device, namely a so-called cavity, enclosing the loose piece with a clearance. Instead of using a piece of metal or rubber which is unfixed and therefore loosely inserted in the cavity it is also common to use an elastomer diaphragm as a loose piece. Such a diaphragm is thin, also partly reinforced and vibratory. However, according to the state of the art said loose pieces are disposed in cavities of the aforementioned kind to limit the vibration of such uncoupling diaphragms to a certain deformation path corresponding to the low amplitudes of the vibrations to be uncoupled and the path-length thereof. Accordingly, the term xe2x80x9cloose piecexe2x80x9d used in the following comprises, besides uncoupling elements being unfixed in path-way limiting cavities, also uncoupling diaphragms of the aforementioned kind.
Furthermore, in the field of automotive engineering numerous means to expand the field of use and to improve the comfort of uncoupling or not uncoupling hydraulic bearings are known, which act upon the damping fluid and change the bearing characteristics thereby. Said means are, however, mostly devices which affect the damping fluid by means of rheological, hydraulical, configurative vibrational, mechanical or pneumatical regulation and compensation forces.
In this context propositions have been known for a long time to change the characteristics of hydraulic bearings during their use, i.e. during the dynamical loading of the hydraulic bearing, in a more effective way by damping or absorbing unwanted vibration introduced into the bearing by means of pneumatic compensation. In recent years this has all the way been accomplished by pneumatically acting on the outer side of a compensation diaphragm bounding a compensation chamber. The diaphragm normally does not influence the damping performance, and the characteristics of a hydraulic bearing. Thus, contrary to its original destination as a spring, the compensating diaphragm is remodelled to a component of the bearing significantly modifying the bearing characteristics. In case of unwanted high amplitude vibrations for example it stiffens the spring and in case of unwanted low amplitude vibrations it flattens the spring characteristic curve. This pneumatical effect can be realized by means of compression as known for example from DE 32 10 731 A1, however, it is also possible to use a depression regulation as disclosed in EP 851 146 A1.
Commonly known pneumatically controllable hydraulic bearings are, however, luxury articles regardless of their functional capability. They require complicated real time controlling systems. Additionally, in order to generate the required forces for the compensation diaphragm with its relatively large surface area pneumatic compressors, buffer tanks and switching systems are needed which are dimensioned in a way that these means have to be located outside the hydraulic bearing to be controlled since it is not possible to integrate them in the limited space of such bearings.
Starting from the state of the art described above it is an object of the invention to provide a hydraulic bearing especially an power unit bearing for automotive engineering which is practical with respect to its size, cost and power, which allows for a reduced pneumatic expense and which provides a spring characteristic which can be influenced effectively.
The invention solves this problem by an elastic bearing providing the features of claim 1.
It is an essential feature of the invention that the pneumatic switching of a hydraulic bearing which is constructed in a classical way is not achieved by acting on the compensating diaphragm but by acting on the uncoupling element especially on an uncoupling diaphragm, namely a loose piece. This allows for a reduction and minimization of the required pneumatical expense especially with respect to the required size of the pneumatic component.
According to an embodiment this basic idea of the invention is further developed and instead of using a compensation control much more simple and practical means are provided replacing the control by an adjustable setting of three different operation states of the bearing in order to set the dampening function of the hydraulic bearing to SMOOTH, MEDIUM-HARD and HARD. It is generally sufficient that the three adjustable dampening states are predetermined by the driver at the console of an automobile. In case the automobile is equipped with a sensor technology the three states of the hydraulic bearing according to the invention can be switched pneumatically as a result of a read out process of the controller of the automobile. When air is used as a switching medium three dampening states are provided which have an inherent band width and a dynamic to make a real time compensation and its complicated controlling technique needless, even in a conceptional view.
Further embodiments of the invention are objects of the dependent claims.